CHAPTER XLI 



DRYOPTEROID FERNS (II. Aspidieae) 



Under this heading very numerous Leptosporangiate Ferns are grouped, 

 of various habit, many of them creeping with forked branching of the stock 

 (Vol. I, Fig. 32); but many others have the basket habit with ascending 

 stock, as in Dryopteris filix-inas (L.) Schott, which may be taken as a 

 central representative of the group (Vol. I, Fig. 31). The dermal appen- 

 dages of these Dryopteroid Ferns are chaffy scales, often very plentiful and 

 prominent: but associated with them there may be simple or glandular 

 hairs. The leaf-stalk is as a rule not articulate, and the venation may be 

 open or reticulate. The sori are usually of a roundish form, but they commonly 

 show a more or less obvious lop-sidedness, or zygomorphy. They are super- 

 ficial, being sometimes placed terminally but for the most part dorsally upon 

 a vein, or seated at a point where veins meet. An indusium is usually 

 present protecting the mixed sorus: it is of variable form and position in 

 the different types : but often it is feebly developed or even absent. Glandular 

 hairs are frequently associated with the sporangia, which have a vertical, 

 interrupted annulus, and usually a three-rowed stalk. The spores are bilateral, 

 and possess a perispore (Hannig, Flora, Bd. 103, p. 340). 



The adult axis of these Ferns is traversed by a simple dictyostele, typically represented 

 for the larger upright stocks by the well-known reticulum of the Male Shield Fern (Vol. I, 

 Fig. 140). The highly disintegrated leaf-trace here possesses two larger adaxial marginal 

 strands, marking the heel of the horse-shoe, and a varying number of smaller strands, 

 forming the usual abaxial curve between them. But in the smaller creeping forms, where 

 the leaves are alternate and remote, the dictyostele of the axis may appear simplified down 

 to three or even two meristeles, placed respectively above and below, with the alternate 

 and greatly elongated leaf-gaps separating them. This is found in the Oak Fern, and the 

 Beech Fern (Luerssen, Rab. Krypt. Flora, ill, pp. 297, 301). It is plainly an adjustment 

 according to habit and actual size. 



The leaf-trace is variable in its complexity along lines parallel to those of the axis : the 

 results of the observations of Luerssen may be extracted for certain familiar Ferns of this 

 affinity, and tabulated as follows: 



A. Relatively simple : two strands pass separately into the rachis, but fuse upwards 

 to form a gutter-shaped meristele, as in Athyriiim filixFoemina (Luerssen, I.e. 

 p. 130, Fig. 90). 



Dryopteris Linnaeatia C. Chr. Oak Fern. 

 Dryopteris Phegopteris (L.) C. Chr. Beech Fern. 

 Dryopteris thelypteris (L.) A. Gray. IVIarsh Buckler Fern. 

 Dryopteris oreopteris (Ehrh.) Maxon. Mountain Buckler Fern. 



